New Delhi: As the burden of atrial fibrillation (AFib) in India makes it an important health issue, the Cupertino-based iPhone maker on Thursday brought its much-anticipated ECG app and irregular rhythm notification feature to Apple Watch users to India.

Available with an update to watchOS 6 on Apple Watch Series 4 and later, the ECG app and irregular heart rhythm notification feature will help users identify signs of AFib, the most common form of irregular rhythm.

"We are confident in the ability of these features to help users have more informed conversations with their physicians," said Sumbul Desai, MD, Apple's Vice President of Health.

"With the ECG app and irregular rhythm notification feature, customers can now better understand aspects of their heart health in a more meaningful way," Desai added.

AFib can lead to blood clot formation in the heart, leading to stroke. It is more prone in those patients who are predisposed to having AFib and stroke.

According to Dr Devi Shetty, Chairman and Executive Director of Narayana Health, devices like Apple Watch will help users have better conversations with their doctors.

"It will open the door for a big shift in monitoring an individual's heart health," said Shetty.

New electrodes built into the back crystal and Digital Crown on Apple Watch Series 4 or later, work together with the ECG app to enable customers to take an ECG similar to a single-lead reading.

To take an ECG recording at any time or following an irregular rhythm notification, users open the new ECG app on Apple Watch Series 4 or later and hold their finger on the Digital Crown.

As the user touches the Digital Crown, the circuit is completed and electrical signals across their heart are measured.

After 30 seconds, the heart rhythm is classified as either AFib, sinus rhythm or inconclusive.

All recordings, their associated classifications and any noted symptoms are stored securely in the Health app on iPhone.

Users can then share a PDF of the results with their physicians.

With watchOS 6, the irregular rhythm notification feature will use the optical heart sensor to occasionally check the user's heart rhythm in the background for signals of an irregular heart rhythm that appears to be Afib.

If irregular heart rhythm such as Afib is identified on five rhythm checks over a minimum of 65 minutes, a notification will be generated to alert the user.

The ECG app's ability to accurately classify an ECG recording into AFib and sinus rhythm was validated in a clinical trial of around 600 participants.

The study found the ECG app on Apple Watch demonstrated 98.3 per cent sensitivity in classifying AFib and 99.6 per cent specificity in classifying sinus rhythm in classifiable recordings.

The irregular rhythm notification feature was recently studied in the Apple Heart Study. With over 400,000 participants, the Apple Heart Study was the largest screening study on atrial fibrillation ever conducted.

A subset of the data from the Apple Heart Study was submitted to the FDA to support clearance of the irregular rhythm notification feature.

In that sub-study, of the participants that received an irregular rhythm notification on their Apple Watch while simultaneously wearing an ECG patch, 80 per cent showed AFib on the ECG patch and 98 per cent showed AFib or other clinically relevant arrhythmias.

There have been several examples where Apple Watch saved lives. A US doctor saved a person's life by using Apple Watch Series 4 on his wrist to detect atrial fibrillation at a restaurant.

An Apple Watch user in the UK was recently alerted about his low heart rate by the device. It revealed a serious heart condition that ultimately resulted in a surgery to fix the problem.

There is a dearth of data on epidemiologic outcomes in patients of Afib in India, leading to inconsistent practice patterns as regards to medical therapy, and Apple Watch data can help in this direction, feel experts.